The present invention relates to prefabricated pyramid-shaped structural members for three-dimensional structural members, the frameworks consisting of rod members connected with each other at their base, the rod members being for instance profile bars, and of which diagonally running rods extend toward the vertex of each structural member, which are connected with a joint member, wherein each joint member includes a plurality of tapped boreholes for the screw connection of other rods of the total three-dimensional framework.
It is known to manufacture such pyramid-shaped structural members in the form of prefabricated structures and to join them together at the building construction site in connection with additional rods, forming a three-dimensional checkerwork grilling in two layers. Such checkerwork grills, for instance, may form supporting structures for roofs used for various purposes. Until this time, when these three-dimensional structural members have been used, the ends of the diagonally running rods have been connected at the vertex of the pyramid-shaped members by means of weld connections formed with joint members. This methods, however, has the drawback that the pyramid-shaped structural members and the joint members cannot be produced independent of each other but must be single integral members, although their separateness would be very desirable from the point of view of manufacturing technology.
As a result of these conditions, until this time it has been necessary for instance for the surface treatment, including the treatment of the hot galvanizing of the pyramid-shaped structural members, to go to the bother of closing off the tapped boreholes in the joint members, in order to prevent the running on and continuation of these tapped boreholes through the surface protective layer, for instance a layer of zinc. In addition to that, following the successful welding of the joint members with the ends of the diagonally running rods, an eventual, expected and still required adjustment of the axes of the tapped boreholes in the joint members which would occur during the assembly and relative to the pyramid-shaped, rod-shaped structure is no longer possible.